KerbalX

Credit to CommiKiller76 for making the cover image

That’s right, I’ve done it again. I’ve made another super fast and very ugly plane. This is an improvement on my last craft, which was incredibly fast. Well, this one’s faster. It’s in the name. It can get more than 6 km/s near sea level, and just gets faster as you climb.
The description will be very similar to before, as the main difference is in the wing structure and maneuvering performance

The powerplant for this ridiculous beast is the hopes and dreams of young Kerbals everywhere (every time a child Kerbal stops believing, one of these suffers an engine failure) [docking ports]. This aircraft is capable of accelerating at roughly 15Gs. Its top speed increases as it gains altitude, and it can fly faster than Mach 18 at low levels.

To control throttle, zoom into the craft. The active docking ports are on the CoM, so you should zoom right into them.

You can land anywhere using the handy landing legs that come pre-installed. To prevent unplanned celebratory fireworks, it is advised to fly at less than full throttle, or to turn reentry heating down in difficulty settings.

Because the propulsion doesn’t need such silly things as air or your approval, you can take this thing into space. That’s right, it’s an SSTA that can perform massive burns super quickly.

Like my previous record, this is configurable. If you want, you can give it FAT-455s or Big-S wings and it’ll pull an insane number of Gs in a turn. Though I don’t know why you’d do that when the current configuration is faster

Oh and good luck hand-flying this thing. I’d use AtmosphereAutopilot if I were you.

Mileage may vary, but I was able to get about 6250 m/s at 1km, 30km/s at at 10km, and an astonishing 54.3 km/s around 26.5 km in altitude.

Let’s put that speed into perspective, shall we?
LA to NYC is typically a 5h 20m flight. This thing can fly that in less than 72 seconds (ignoring how long it takes to accelerate or slow down to land)
NYC to Paris is 7hr 25m. In this, it’s only 107 seconds.
The longest commercial air route that I found is Singapore to NYC, at a total of 18hr 40m. This can fly it in less than five minutes (4:22, to be exact). That’s fast.

*To measure top speeds, I increased gravity by a lot. Doing so decreased drag, as this thing goes so fast it needs to constantly pitch down to avoid climbing rapidly. Data valid for the given configuration only, and not for any configuration with different wings or landing gear